Unset a specific variable within a multidimensional array

Question

I can't figure out how do this at all. My first attempt involved using references and calling unset on a reference simply unlinks the reference. I tried recursion but couldn't get it to work, I then tried array_walk and array_filter without success. Here is a simple example that demonstrates what I am trying to do.

<?
class Sample {
    //Please note this can have a completely variable amount of vars/dimensions
    $data = array("system" => array("value1","value2"), "session" => array("value1"));

    public function erase($value){
         //Here I am suppose to somehow delete that exists in $this->data
    }
    public function display(){
         print_r($this->data);
    }
 }


 $Sample = new Sample();
 $Sample->erase(array("system","value1"));
 //I am extremely flexible on the format of the erase parameter ($value)
 $Sample->display();

 should output with the variable unset($this->data["system"]["value1"]) :

 array("system" => array("value2"), "session" => array("value1")

Ohgodwhy helped by creating a eval.in with a slighly modified example

Thank you for your help

Adam Sinclair · Accepted Answer · 2014-09-23 19:46:10Z

I've made this function and work pretty great.

function erase(array &$arr, array $children)
{
    $ref = &$arr;
    foreach ($children as $child)
        if (is_array($ref) && array_key_exists($child, $ref)) {
            $toUnset = &$ref;
            $ref = &$ref[$child];
        } else
            throw new Exception('Path does\'nt exist');
    unset($toUnset[end($children)]);
}

Example 1:

Here's an example of how you would unset $arr['session']['session3']['nestedSession2']

$arr = [
    "system" => [
        "system1" => "value1",
        "system2" => "value2"
    ],
    "session" => [
        "session1" => "value3",
        "session2" => "value4",
        "session3" => [
            "nestedSession1" => "value5",
            "nestedSession2" => "value6",
        ],
    ],
];

print_r($arr);
erase($arr, array('session', 'session3', 'nestedSession2'));
print_r($arr);

Example 2:

It can even unset a whole nested array, here's how you would do it (handling errors):

print_r($arr);
try {
    erase($arr, array('session', 'session3'));
}  catch (Exception $e) {
    echo 'Caught exception: ',  $e->getMessage(), "\n";
}
print_r($arr);

Example 3:

It also work with non-assiociative array:

$arr = array('fruit1', 'fruit2', 'fruit3');
print_r($arr);
try {
    erase($arr, array(0));
}  catch (Exception $e) {
    echo 'Caught exception: ',  $e->getMessage(), "\n";
}
print_r($arr);

Example 4:

In case of error:

$arr = array('fruit1', 'fruit2', 'fruit3');
print_r($arr);
try {
    erase($arr, array('pathThatDoesNotExit'));
}  catch (Exception $e) {
    // do what you got to do here in case of error (if the path you gave doesn't exist)!
    echo 'Caught exception: ',  $e->getMessage(), "\n";
}
print_r($arr);

Thanks so much! It was my understanding (and I even coded an example that provided it) that doing an unset on a reference causes it to simply unlink the reference (not delete the item). How does your code get around this?
@hendr1x By passing by reference you can, inside the function, unset an element of an array. However unset($theWholeArray) inside the function won't do work.

Ohgodwhy · Accepted Answer · 2014-09-23 18:24:08Z

1

If you'll always be passing in the key name of the array that contains the value, followed by the value, we can use array_search to perform this.

if(false !== $key = array_search($value[1], $this->data[$value[0]])):
    unset($this->data[$value[0]][$key]);
endif;

Here's your eval.in example

answered Sep 23, 2014 at 18:24

Ohgodwhy

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3 Comments

hendr1x Over a year ago

Thank you for your help. Unfortunately I need the erase method to be flexible to handle any number of dimensions/variables and values (including associative arrays) ( eval.in/197702 )

Ohgodwhy Over a year ago

@hendr1x Okay, then how are you going to pass along arguments? Do you just want to search all arrays for a value then get it's key and unset it? Do you want to pass in the subarray? etc..

hendr1x Over a year ago

I am really flexible on how the system works. Adam posted work code that took an array("level1","level2","level3"). If you want to discuss I'll keep checking. Thanks for your help.

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